1. Field of the Invention
The present invention relates to an apparatus for placing spacer sticks between layers of lumber as the layers of lumber are stacked.
2. Description of Related Art
In the lumber industry green cut lumber is normally dried by forming the lumber into stacks which are then subjected to a drying process. In preparation for the drying process the lumber is first sorted into uniform sizes and then the lumber is arranged into layers. The layers of lumber are then stacked on top of each other with spacer or separation sticks being placed between the layers of lumber. The spacer sticks are elongated pieces of wood with rectangular cross sections. In the past it has been the practice to place the spacer sticks on each layer of lumber manually. Typically, the sorted lumber that has been arranged into a package is sent to a stacking machine. The stacking machine functions to make a single layer of lumber generally eight feet wide and, depending on the length of the lumber, about six to twenty four feet long. The stacking machine will place each layer on top of one another, on an auto indexing, downward moving stack support.
The separating sticks, used in-between each layer lumber would be set in manually by 2-6 workers depending on the length of the lumber and the users desired cycle time for each stack of lumber. The stick placing personnel stand opposite the direction of travel of the layer of lumber. The personnel set in place sticks that are xc2xexe2x80x3 thick by 1xc2xdxe2x80x3 wide by 8 feet long, approximately one to two feet apart, on each layer of lumber. This is repeated until the stack reaches maximum height. Once maximum height is reached, the finished stack of lumber is removed from the stack support and a new stack is started.
Keeping the above process in mind, it is hard if not impossible to obtain consistent, repeatable performance from personnel having varying physical abilities and levels of experience. This inconsistency in performance has an adverse effect on the total output of industrial operations. Furthermore, personnel are in a semi-hazardous position as lumber being stacked has a tendency to skew, fall, or move without warning. Personnel have and do continue to be injured in this process.
For the foregoing reasons, machines that automatically place spacer sticks on layers of lumber have been proposed in the art. Listed below are some examples of stick placing machines that have been proposed in the art. U.S. Pat. No. 1,705,570, issued to Frederick W. Horstkotte on Mar. 19, 1929, U.S. Pat. No. 3,738,510, issued to Howard C. Mason on Jun. 12, 1973, U.S. Pat. No. 4,229,133, issued to Charles L. Johnson on Oct. 21, 1980, U.S. Pat. No. 4,324,520, issued to Jan E. Kjellberg on Apr. 13, 1982, U.S. Pat. No. 4,610,360, issued to Hasse Forslund on Sep. 9, 1986, U.S. Pat. No. 4,801,233, issued to Edward Ritola on Jan. 31, 1989, U.S. Pat. No. 4,810,152, issued to Larry A. Gillingham et al. on Mar. 7, 1989, U.S. Pat. No. 4,878,803, issued to Wade Q. Whiddon on Nov. 7, 1989, U.S. Pat. No. 5,350,272, issued to William P. Bowlin on Sep. 27, 1994, U.S. Pat. No. 5,636,965, issued to William R. Newnes et al. on Jun. 10, 1997, Canadian Patent Number 875941, issued to Ray W. Newnes et al. on Jul. 20, 1971, and Canadian Patent Number 955970, issued to Alpo Rysti on Oct. 8, 1974, all show machines for placing spacer sticks in stacks of lumber. U.S. Pat. No. 3,894,625, issued to John S. Boyle et al. on Jul. 15, 1975, shows a lumber sorting system with overhead feed.
The automated stick placing machines proposed to date suffer from the drawback that these machines are not very tolerant of sticks that may be slightly warped. In other words, the machines proposed to date require sticks that are very straight and flat in order to feed into the machine without causing malfunctions. Therefore, the need persists in the art for a stick placing machine which is tolerant of slight warpage in the sticks being fed into the machine. Also, the need persists for a stick placing machine that can be retrofitted to existing lumber stacking machines and that is modular in construction to allow the machine to be custom tailored to a user""s needs without having an exorbitant price.
None of the above inventions and patents, taken either singly or in combination, is seen to describe the instant invention as claimed. In particular, none of the above references teach or suggest the unique structural features of the stick placing machine of the present invention. Further, none of the prior stick placing machines are capable of reliably setting in place, between layers of lumber, warped, twisted, crooked, and/or bowed separation sticks (as allowed by the requirements of the particular type of stacking operation) and also rejecting separation sticks whose condition is not in compliance with the applicable restrictions regarding acceptable stick conditions.
The present invention is directed to an apparatus for placing spacer sticks between layers of lumber as the layers of lumber are stacked. The present invention includes an overhead feed system for distributing spacer sticks to a plurality of stick placement modules. Each stick placement module has an internal chain conveyer system which carries spacer sticks from the overhead feed system to a positioner system which positions the spacer stick such that the spacer stick can be grasped by a plurality of stick placement arms. The stick placement arms have pneumatic or hydraulic cylinders which allow the stick placement arms to extend and retract. One end of each of the placement arm cylinders is pivotally supported within the respective stick placement module. The pivotally supported end of each placement arm cylinder is allowed some travel along the direction of the longitudinal axis of the placement arm cylinder. The placement arms are mounted such that they extend downward to make contact with and grasp the spacer stick. Contact with the spacer stick is detected when the pivotally supported end of each placement arm cylinder manifests some movement along the direction of the longitudinal axis of the placement arm cylinder, and further extension of the placement arm is stopped upon detection of contact with the spacer stick. The pivotal mounting of the placement arm cylinders allows the longitudinal axes of the placement arms to deviate from the vertical as required for grasping the spacer stick. The placement arms"" deviation from the vertical and the amount of extension of each of the placement arms are indicators of the warpage in the spacer stick. The spacer stick is rejected if the deviation of the placement arms from the vertical and/or the amount of extension of the placement arms, relative to the amount of extension of the placement arms for grasping an unwarped spacer stick, is beyond tolerable limits.
Accordingly, it is a principal object of the invention to provide an apparatus for placing spacer sticks between layers of lumber.
It is another object of the invention to provide an apparatus for placing spacer sticks between layers of lumber which is modular in construction.
It is a further object of the invention to provide an apparatus for positive delivery of the spacer sticks to their destination module and ultimately to the correct position on the lumber.
It is a further object of the invention to provide an apparatus for placing spacer sticks between layers of lumber which can be retrofitted to existing lumber stacking machines.
Still another object of the invention is to provide an apparatus for placing spacer sticks between layers of lumber which is capable of automatically rejecting spacer sticks which fail to meet applicable requirements.
It is an object of the invention to provide improved elements and arrangements thereof in an apparatus for the purposes described which is inexpensive, dependable and fully effective in accomplishing its intended purposes.
These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.